Semiconductor light-emitting devices including light emitting diodes (LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavity laser diodes (VCSELs), and edge emitting lasers are among the most efficient light sources currently available. Materials systems currently of interest in the manufacture of high-brightness light emitting devices capable of operation across the visible spectrum include Group III-V semiconductors, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen, also referred to as III-nitride materials. Typically, III-nitride light emitting devices are fabricated by epitaxially growing a stack of semiconductor layers of different compositions and dopant concentrations on a sapphire, silicon carbide, III-nitride, or other suitable substrate by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques. The stack often includes one or more n-type layers doped with, for example, Si, formed over the substrate, one or more light emitting layers in an active region formed over the n-type layer or layers, and one or more p-type layers doped with, for example, Mg, formed over the active region. Electrical contacts are formed on the n- and p-type regions.
FIG. 1 illustrates a lighting apparatus described in more detail in US patent application 2011/0227477. The device of FIG. 1 includes a submount 100 with a light source (e.g., an LED) mounted thereon. Paragraph 54 of US patent application 2011/0227477 teaches “First emissive layer 110 is disposed above the second emissive layer 115 and receives at least a portion of the radiation emitted from the light source 105. Second emissive layer 115 is disposed between the conventional base LED 105 and the first emissive layer 110. The second emissive layer 115 receives at least a portion of the radiation emitted from the light source 105. An optional encapsulant resin 120 is placed over the light source 105, the first emissive layer 110 and the second emissive layer 115. In some embodiments, the first emissive layer 110 and the second emissive layer 115 are fixed together to form a composite.”
Paragraph 60 of US patent application 2011/0227477 teaches “The lighting apparatus can include a first emissive layer having a first garnet phosphor and a second emissive layer having a second garnet phosphor . . . . The emissive layers may, in some embodiments, be ceramic plates . . . . The ceramic plates may be fixed together to form a composite.”